- With scores of species of lupines, it's difficult to prescribe precise care for plants since some species native to colder, drier climates may need different care compared to those native to subtropical lands. Overall, all lupines perform best when grown in full to partial sun and in moderately fertile, light-textured soils that are slightly acidic in pH. A moist, well-drained soil from spring to fall frost is perfect, with slightly drier soil during the winter dormancy. Overall, lupines grow best in regions where summers are cool to warm and not overly humid. However, some species or hybrids demonstrate a better tolerance to winter cold or summer heat and humidity.
- Even with the best of care and maintenance, garden-grown lupines may not persist long as perennials but act more like annuals or biennials. In U.S. Department of Agriculture plant hardiness zones 6 and warmer, the summer heat causes most lupines to wither or falter and not look their finest. Add in oppressive summertime humidity, such as in the Southeast, and plants tend to die out by early fall. To perpetuate lupines in the garden, it's worthwhile to propagate by sowing seeds or by making cuttings from stem bases in mid-spring, according to the American Horticultural Society's "A-Z Encyclopedia of Garden Plants."
- Allow lupine plants to grow without pruning or disturbance in the garden. There's no need to fertilize or overwater them. Do not break off or prune back any green vegetation, as it reduces the carbohydrates make in photosynthesis. Weakened plants do not bloom as well. After blooming, you may cut off the old flower spikes to tidy the look of the plant, but this eliminates any seed production to create new plants. Once fall frost kills back foliage, you may cut it off at ground level but keep any low rosette or tuft of green leaves intact to potentially survive over winter. Lupines overwinter better if the soil is not wet during the dormancy.
- If old flower spikes remain on the lupines heading into the heart of summer, seeds develop into pods that then open to shed seeds to the ground. These seeds will sprout in winter or spring once they've been treated with cold. If you harvest seeds, there are two options to increase germination. Nick the hard seed coat with a paring knife and soak the seed in water for 24 hours before sowing. Alternatively, expose the seeds to four to six weeks of temperatures between 30 and 40 degrees Fahrenheit in a plastic bag or lidded jar with damp paper towels or peat moss in the refrigerator. Seeds sown in early fall sprout and grow leading into winter and again in early spring, potentially blooming later that spring. Although seeds do not produce the same colored flowers as the parent plant, letting seeds grow in the garden ensures lupines persist year after year.
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